Apparatus for accelerating charged particles



e L.. Regan,

3 Sheets-Sheet l APPARATUS FOR ACCELERATING CHARGED PARTICLES Inventors u, m K R d P a W o H n) O S w a L. S e m Dec. 16, 1952 Filed NOV. 18, 1950 ma N /vw 1.3 N

T h ei 1^ Att ornay.

De@ 16, 1952 J. L. LAwsoN ETAL 2,622,194

APPARATUS FOR ACCLERATING CHARGED PARTICLES Filed Nw. 1s, 195o ssheets-sneet 2 r r V o fom w//vaM/es 3 l o www? mwa/Na.: r

F-gga.

& @UTEP W///NGJ' 0 ma Inventors:

I /vcRfAs/Ner James L. Lawson,

Howard R. Kratz, GeorgeLRagan, /Mvsn wma/Nas l by )QJ a m Their` Attorney.

Dec. 16, 1952 J. .-LAwsoN ETAL 2,622,194

APPARATUS FOR ACCELERATING CHARGED PARTICLES Filed Nov. 18, 195o 3 sheets-sheet '5 Figli.

/ SYNC/RO TRO/V STH BLE 088/ 7' REG/0N Figli DELAY l PULSE Inventors:

James L. Lawson, Howard Kratz, George .L..1Qa ga.v\V

by )QJ d. ffy/iw@ Their` Attorney.

8 Ar ons/ML PA TH Patented Dec. 16, 1952 UNITE-D STATES TENT OFFICE APPARATUS FOR ACCELERATING CHARGED PARTICLES James L. Lawson and Howard R. Kratz, Schenectady, and George L. Bagan, Glenville, N. Y., assignors to General Electric Company, a. corporation of N cw York Application November 18, 1950, Serial No. 196,482

(Cl. Z50-27) 11 Claims.

dorp and assigned'to the assignee of this present' invention. Such apparatus is commonly referred to in the art as a betatron and comprises field generating means for providing a time-varying magnetic flux which links the orbital path to accelerate the particles and a time-varying magnetic guide field which traverses the locus of the orbital path for constraining the particles thereto.

It is also known that further energy may be imparted to charged particles such as electrons by subjecting them to the repetitive action of a localized cyclically-varying electricfield after they have been accelerated to a desired energy level by the above-mentioned betatron apparatus. Suitable apparatus for achievingr this purpose is disclosed in U. S. Patent 2,485,409, granted October 18, 1949, to Herbert C. Pollock and Willem F. Westendorp and also assigned to the assignee of this invention. This latter apparatus may be referred to as synchrotron apparatus utilizing betatron start. means such as a high frequency resonator coupled to the charged particle orbital path for applying a localized cyclically-varying electric field to accelerate the particles after they have been preaccelerated by betatron action, and means for producing a time-varying magnetic guide field traversing the locus of the orbital path for constraining the particles thereto during the application of the electric field.

Both of the above-mentioned forms of apparatus for accelerating charged particles commonly employ an iron core for the production of the proper magnetic fields and fluxes. Because such an iron core must be laminated to minimize the generation of eddy currents and has great weight, fabrication and handling present major problems. Moreover, it is very difficult to eliminate azimuthal eld asymmetries, and the limitations upon magnetic induction imposed by saturation of the iron necessitate large amounts of stored energy in the accelerator apparatus. As is disclosed in U. S. Patent 2,465,786 to John P. Blewett, the disadvantages represented by the It generally comprises` iron core may be obviated by `the expedient .of producing the desired magnetic fields and fluxes with non-ferromagnetic field generating means.

In the construction of non-ferromagnetic synchrotron apparatus utilizing betratron start, it is desirable that the magnetic eld and flux generating means should couple as closely asv possible with the charged particle orbital path so that energy need not be stored in a greater volume of space than necessary. This is particularly desirable in connection with thev magnetic guide field which is provided during the period of synchrotron acceleration, because the magnetic field intensity of magnetic induction required during that period to retain the charged particles within the orbital path is much greater than the magnetic eld intensity required during the betratron start period. It is also desirable that the stable region, or the region surrounding the orbital particle path within which proper acceleration can occur, be as large as possible duringthe betatron start period in order to increasev the total number of charged particles which may. be accelerated, to reduce loss of charged particles. due to scattering to the walls of the apparatus,f.

and to render less serious the presence of small eld inhomogeneities. period of acceleration, these latter undesirable effects are not excessively bothersome because, during the betatron start period, the amplitude of the charged particle oscillations about the stable orbital path decreases considerably.

In accordance with the present invention, there is provided improved non-ferromagnetic charged. particle accelerating apparatus which comprises non-ferromagnetic field generating means enclosed by a metal tank adapted for internal evacuation. The field generating means includes two ment of the synchrotron guide field windings ina region closely adjacent the stable orbital path whereby the energy stored in the synchrotron eld may be minimized. Furthermore, since the betatron and synchrotron field generating means include separate windings, they may be separately energized thereby permitting the arrangement of a much slower rate of rise for the betatron iield andflux to reduce eddy field disturbances and.'

During the subsequent.

Other objects and advantages of this invention will be apparent from the followinggdescriptionf taken in connection with the accompanying" drawings in which Fig. l is a sectionalized elevation of non-ferromagnetic synchrotorr apparatusv suitably embodying the invention'and taken along' line I-I of Fig. 2; Fig. 2 is afsectionalized view taken along line 2-2 of Fig. l; Figs. 3, 3a, 4 and 4a are graphical representations .usefull in: explaining the invention; Fig. 5 is a schematic diagram showing exemplary-circuit connections for energizing the apparatus of Figs. 1 and 2; and

Fig.' 6is 'anothergraphical representation useful l inexplainingthe invention.

Referringnow to Figs. land 2, there is shown non-ferromagnetic charged particle accelerating apparatus comprising an air-tighttank I`which may be evacuated through a suitable connection` 2 attached tothe baseplate 3of tank I. Base plate 3j and a cover plate 4' may be retained in air-tight relation with respect to a cylinder 5`by means of a' plurality4 of peripherally spaced'screws 6 insertedthroughcircular gaskets?,` which mayY consist ofy a suitable syntheticrubber material. Baseplat'e 3, cover 'plate Il, and cylinder 5, which define chamber 5", must'be of suicient thickness to'withstandinternal evacuation without serious deformationL and, therefore, should consist of a high tensile strength material, such as steel'or 1IOI1.'

Supported from thebasefplate 3 by means of circular' dielectric spacer members 3 and 9 is a liner`I gthefunction of which will be morefully described hereinafter; Liner IE)V preferably con- SistsA of" a highly' conductive non-ferromagnetic materiali-such as copper and comprises a' base plateY II, a" cover plate I2A and a hollow cylinder I3; Base-plate I-I- and cover platel I2 are attached` to' cylinder I3 by means of a'4 plurality of'peripherally spaced screwsl Ill,V andan orifice I5isprovided'in base plate I I vtopermit internal evacuation of linerI through connection 2. For

thesakeI of symmetry, an orifice I Sis situated in cover plate '|21 In order' to provide vfor the injectionv of charged p particles such'as electrons for'accelerationwithin liner I Il, there is'shown a source assemblyv I6 which mayicomprise an electron gun I1 having a lamentary cathodeY (not shown) suitable for injecting, in response to intermittent energization, a; burst of electrons into the stable particle orbit indicated' at point x. Structural details for gun I7, which may be advantageously employed in connection with the present invention, are disclosed and claimed in U. S; Patent 2,499,192, granted February 28, 1950 to James M. Lafferty and assigned to the assignee of' the'presen't invention. Gun Il may be supported'within' a hollow'tube I'of a low-conductivity, non-ferromagnetic material such as stainless steel' and energized through conductors (not shown) insulatingly introduced through tube I Si A slotrIS is F provided in the lower end of tube l5 to permit the egressof electrons from gun I'I. Tube I8 is flared out-wardly at'itsiupper'end to: receive in hermetic relationship: an insulator I 9 and yis also HermeticallyY sealed" adjacent its upper: end to a cylindrical membersk 55: may be imparted to spokes 53'by means of' base member 2i). An apertured plate 2| is held by means of screws 22 against a boss 23 upon insulator I9 to compress packing material 24, thereby assuring a vacuum-tight relationship. In order to permit adjustment of the position of gun' l? withinliner Iii, basev memberY 2ilis supported by a flexible bellows '25 which is sealed at its lower end to the outer surface of tank I by=means of an apertured plate 26, a compressible gasket--2fl`and .screws 28. The position of gun Il iswmaintained by means of a stud 29 and nuts 36, the latter of which may be screwed up or downto adjust'bellows 25. Several studs 29, alongjwith nuts'i, may be located around the vperiphery-of,base-rnember 29 to insure desired positioning of 'gun I7.

A'sfzhas beenzmentioned heretofore, the present invention, contemplates the initial betatron acceleration' of injected charged particles with nonferromagnetic iield generating means capable of supplying both ay timevarying magnetic flux which linksthe orbital path of the charged particles to impart acceleration thereto andiatimevarying magneti-c guideeldwhich ytraverses the orbital pathv for the lpurpose of 'constraining the charged particles thereto. Accordingly, betatron windings 3|, 32,-' SB'and 34 are shownr positioned adjacent the crbitalpath indicated4 at point zc. Thepair ofv windings 32 and. 331i haveafdiam.- eter greaterthan orbitalpath'" .rwhile' the pair of Vwindings 3i and 3'll.liave a lesserdiameter. These windings comprise'. a pluralityof circular hollow tubes 'S5-'throughWhich'a suitable' coolant such as water maybe circulated." Windings 3|;

" 32'; 33` and'fare seriesiconnected'andenergized through hollow tubularv conductors SS'by asuitable source ofivoltage (notshown) suchzthat the current through allfthe windings ilows in the same directionfor a purpose to` be: more fully describedhereinafter.. Conductors Sea-ret hermetically sealed within: tank Ibymeans ofgin'.-

sulators 3l', apertured'plates, screwsf and;-

packing materiall di). Tb.: prevent a' conductive connection to line lil, conductors 36 /arefinsertedf therein through; apertures 4I.

Windingsl, 32; 'and 3Q are respectively supported from base plate II of liner le 'by meansof :dielectric spacers 42, coil supports-e3; lill; 45 andli', cylindricallyshaped spacer members @Tand lland dielectricv shimming membersvv 9, Sil; 5I' and 52".

To assure theretention of' proper positioning of vfield generating `windings 3|', 32, k33 and 314, aswell as ofA othercomponents ofthe accelerat` ing apparatus, during operational vperiods when tremendous forces are exerted thereupon due-.to

the magnetic fields and fluxes which are gene erated', various support members are provided. These members include dielectric spokes 53'which bear at their'outer ends against'flanged'hollow Outward radial thrust spreaders 551 Spreaders 56 comprisev lower beveled cylindrical dielectric blocks EI'having studs E'B'eXtending therefrom. Upper dielectric cylindrical beveled blocks 59 are apertured to permit the extension therethrough of studs 'and'block' lindrical spacer members 6:3;and64fareemployed in connection with spreader members 65, which are similar to the above described spreader members 56 and comprise upper and lower blocks 66 and El, studs 68, and nuts 69.

The dielectric materials utilized to form the various above-mentioned supports must be able to withstand the tremendous forces which are exerted thereupon Iwhen the accelerating apparatus is in operation. Furthermore, the large bulk of material in the supports must have a relatively low vapor pressure to permit successful evacuation of tank l and liner l0. It has been found that the cylindrical supports may be advantageously constructed by winding glass cloth, which has been impregnated with a suitable organic resin, around a steel mandrel having a desired shape.` After the desired form has been obtained in this manner, the support may be cured and stripped from the mandrel in a manner well known to those skilled in the art. Subsequently, the support may be machined to the desired dimensions. A suitable organic resin may consist of diallyl phthalate and diethylene glycol maleate along with a polyvinyl formal resin obtained by the partial hydrolysis of polyvinyl acetate 4and the reaction of the partially hydrolized product with formaldehyde.

It will now appear that, if the betatron field and iiux producing windings 3l--34 are energized from a source of time-varying voltage in a manner to be more fully described hereinafter, acceleration in an orbital Ipath of -charged particles injected from gun l1 may be obtained, providing the well known betatron iiux and field considerations are satisfied. 'Ihe betatron relationships which must be met are as follows:

where Ae is the total change in flux linking the vorbit from the time at which t-he magnetic induction B is zero, ro is the radius of the orbit, and Bn is the magnetic induction at the orbit;

Mer

where n is an exponent having .a value between 0 and 1, B is the magnetic induction at a position under 4consideration and r is the radius of such a position. Equation y1 represents the flux-field condition which must be complied with to secure successful acceleration, and Equation -2 represents a stability condition which must be fulfilled before the charged particles will execute stable oscillations in the vicinity of the orbital path. In order to satisfy Equation 1, which need be met only along the stable orbit x, with two windings outside and two windings inside stable orbit a: as shown, it is necessary to have the current flowing in all the windings in the same direction, whereupon the flux linking the orbital path is then in the same direction fro-mbothinner and outer windings while the field traversing the orbi-tal path from the inner windings is opposite that from the outer windings. With the proper ratio of the number of turns in the outer windings to the number of turns in the inner winding, Equation 1 can be fulfilled. Equation 2 requires a nearly uniform field which falls off in proportion to l/r" in the region adjacent orbital path x. In 'order to fulfill Equation 2, it is necessary to match the shape of the magnetic induction curves of inner windings 3l and 34 and 'outer windings 32 and 33 such that the net magnetic induction falls `off at the proper rate with the radius in the orbital region. In Fig. 3, curvesf of magnetic induction B in the orbital plane versus radius r are shown for both inner windings 3| and 34 and outer windings 32 and 33. It will be observed from Fig. 3 that the desired falling off of magnetic induction with radius to give a value of n lying between 0 and 1 may be obtained at or near the field maxima oi' both inner and outer windings. This is more clearly shown in Fig. 3a which may be considered as an enlarged view of the right hand portion of Fig. 3.

While it is known that the above stated Equations 1 and 2 both must be fulfilled to obtain betatron acceleration of the charged particles, it has proved to be impractical to calculate accurately the field configurations resulting from windings 3I-34 because of the difficulty of con-- sidering the effect of the liner l0. Liner IIJ, which is employed for a purpose to be more fully described hereinafter, reduces the eld at the orbit and the iiux linking the orbit and also changes the phases of the field and iiux with respect to the current in windings :ll- 34. Consequently, the most effective procedure for loeating windings 3 |-34 has been found to be the employment of various scale models of inner and outer windings whereby the magnetic induction may be measured in a manner well known to those skilled in the art with a magnetic pick-up coil. By successive approximations it is possible to arrive at a geometry which satisfies Equation l along orbital path :c and also produces a satisfactory field variation in both radial and vertical directions over the desired stable region in the vicinity of the orbital path as required by Equation 2. After windings 3|-34 have been installed within liner I0, vertical adjustment to correct for field discrepancies may be obtained by means of shims 49-52. With the above-described winding configuration, a stable region of considerable extent adjacent the orbital path' may be obtained, the shape of such a region being indicated by the solid line representation of Fig. 4.

In the discussion of the production of desired time-varying magnetic fields within the apparatus of the invention, consideration must be given to the problem of their confinement. Externally generated magnetic fields, or ferromagnetic material or conducting material outside the apparatus, cannot be permitted to disturb the fields inside the apparatus, nor can the internally generated fields be permitted to Vdisturb external equipment which is employed in conjunction with the apparatus. Any shielding means that is utilized, however, must not introduce nonlinearities which would prevent procurement of the desired time-varying fields within the apparatus, as would be the case if tank l, which preferably consists of a ferromagnetic conductive material such as iron, were alone employed. Liner IU, which preferably consists of a nonferromagnetic conductive material such as copper, provides shielding of time-varying magnetic elds within tank l without introducing undesired non-linearities. The magnetic shielding action of liner I0 is accomplished by eddy or image currents which flow therein in a direction such as to oppose the time-varying fields which induce them; consequently the time- Varying magnetic fields which would have existed exteriorly of liner I0 during operation of the accelerating apparatus are cancelled, and tank I is prevented from disturbing the internally generated time-varying fields. Liner I 0 and tank I together then serve as effective shields for the apparatus. iriasmuch as tank:- Iv will; criceti-rely shunt direct current; magnetic-,vy fle-lds, which` will not beaffected by liner IB;

After the charged particles have been` acceleratedY to theA desired energy leveli by means ofL betatron fluxV and eld producingV windings 3:l-:f34; further energy may be imparted` toY the particles by means, of a cyclically-varying electric field produced by a highv frequency circuit includinga resonator; l; Resonator 'i0 is ofthe open-circuited-l coaxial line, type in which aV portion;v of an electrostatic shield ll, whose general function; will be more fully described hereinafter, serves asrthe, outer conductor and aV plura-lity of vertical conductors 'l2 serve asthe inner conductor. Both electrostatic shield 'Il and innerzconductors- Z areconstructed of a plurality of separate` wires of a `nonferromagneticv conductive material suchV as copper depending from cover plate IZof liner l as shown, the individual wires being secured together by means of a desired insulatingorganic resin, such as the abovementioned diallyl phthalate and diethylene glycol maleat@ rfjhis construction servesV to minimize the generationnof disturbing eddy currents when the accelerating apparatus is in operation. Within; conductors 'l2 a similar plurality of conductorsfl are provided, which, along with conductors l2, may subtend an arc of about 60 adjacent-orbital path 3c. Conductors 72 and i3 are bent outward at their upper ends and soldered at 'i4 Ito a circular plate 'i5 of a non-ferromagneticv conductive material such as cop-per which is-secured, along with shield il, to cover plater i2 by means of right angle circular clamping members i6 and bolts 7i constructed from a nonferromagnetic conductive material suchas copper. Arcuate dielectric member '1B is positioned within conductors 13 to provide rigidity for the conductorV assembly comprising conductors 72 and '3. Each of the wires of shield 'Il and each of; the conductorsV 72 and '13 may be provided, respectively, with circumferential slots 19, 80 and tilV to interrupt continuous current paths for 4unwanted Veddy currents.

twill now-be observed` that, if resonator it is excited with an energized concentric line s2 hermetically introduced through cover plate il by means of a vacuum-tight bushing 33 and inductively coupled into resonator 'i5 at c, a cyclicalyvarying electric field will be produced between outer conductor TSY and inner conductor l2, such a field ringing out at the ends ofA resonator lo tocouple with the orbital path az. if this electric field is of the proper frequency, energy maybe imparted to charged particles during each revolution within orbital path Assuming that the charged particles are electrons and have been accelerated to approximately the velocity of light withinv orbital path ss by betatron flux and field generating windings S|-34, their approximate frequency f will be given by the following relation:

where c represents the velocity of light. Consequently, the frequency of excitation of; resonator lil. may be arranged at a constant value such that energy is imparted to the charged particlesupon each revolution.

According to the present invention, conductors l2 are provided withextensions $5 extending downwardly and about the charged 'particle orbitalV pathv .1,1 whilev conductors 'i3 terminate vertical extension; abovethe Path as indicated-l This; provides an B.` F. field-free, region- 85, throughout the circumferential extension, ofv conductors 'l2 and 3, such field-free region serving to shield the charged particles from the R. F. elds within resonator 'iii while theyY are within region Therefore, if the frequency of excitation oi;resonator itis equalv to or amultiple of the'frequency given in Equation 3' fory electrons, energymay beimparted tothe electronsf as a function of the time at which they enter and leave resonator 7i).

A better understanding of the mannerin which energy or acceleration isl imparted to velectrons by resonator/'1S may .bei hadby referencezto Fig. 4a wherein,the ;solidfcurvelabeled s, repre,- sentsv the variation with time of the, R.. F. elec;- tric field produced; by resonator lil. If an elec.- tron enters at pointa and leaves at point b; it willV receive an energy increase or acceleration because it entered at a higher positive value-of electric eld than at whichit left. If an electron enters at point c and leaves-at point d, it willreceive essentially no energy increase because thevalne of the electric eld is nearlyY constant over the peak. Therefore, a curve such as dotted curve y may be drawn 'to represent the eiective energy gain or acceleration ofA the electrons. by traversal of resonator lil. It will be seen-that the energy received or given-up by the electrons becomes a function of the drift time or-the time spent within the held-free region 85.

it will be realized that, during acceleration of chargedv particles such as electrons-by thel betatron iux and field generating windings 31;-34 before resonator in is energized, no bunching occurs because acceleration is achieved by means of an electric eld along orbital path :c created by the changing betatron flux linking the path, such a field being essentiallyV circumferentially constant at any given instant'. As a consequence, when resonator 'iii' is energized, electrons enter resonator a' when the electric eld is negative as well as when itis positive; However, due to the phase stability principle announced by E. M. McMillan in the Physical Review, vol. 68, pp. 143-144 (1945), bun'ching, occurs after resonator 'le is energized and, since a time-varying magnetic guide field to be described presently is employed to maintainthe electrons within an orbital path, the bull; oi the electronsv are accelerated or` receive an energy increase as they travel along orbital path in a stable manner.

Of course, charged particles moving along orbital. path :c are affected by any electric held which couples thereto. In order to prevent deleterious results, therefore, it is necessary to shield the orbital path from unwanted electric fields, e. g. those resulting from the electric potentials uponthe various windings within the accelerator apparatus and those derivedv from charges collecting upon parts of the apparatus (especiallyY insulators). Electrostatic shield, 1i, described hereinbefore, acts to perform this function. Shield H may be constructed ohollow wires and water-cooled if excessiveA overheating is encountered. Slots-79, as well asV slots -and el, may not be necessary, providing the respective conductorslie withinclose limits in planes passing through the axisl of the accelerator apparatus.

In order-to provide atime-varying magnetici guide iield to constrain the chargedparticlesto orbital path .r as energy'is being imparted thereto:

by resonator-min accordance with the principles hereinbefore discussed, windings 86, 81, 88 and 89 are disposed adjacent orbital path within circumferential slots in cylindrical spacer members 41 and 48 as shown. Windings 86-89 may comprise a plurality of tubes 90 through which a suitable coolant such as water may be circulated and to which energy may be -supplied through hermetically sealed conductors (not shown) introduced through tank in a manner similar to conductors 36. The magnetic field provided by windings 80-89 must meet the requirements of Equation 2 in that the magnetic guide field within the region surrounding orbit a: must have the desired inverse slope with increasing radius; but the flux generated by windings 88--89 need not meet the requirements of Equation 1 since, during the period of energization of windings 86-89, energy is imparted to the charged particles by means of resonator 'l0 and not by means of a time-varying magnetic flux linking the orbit, as is the case during betatron acceleration. To produce a field complying with Equation 2 alone, a more emcient field producing arrangement may be employed, viz. windings 86-89 may be connected in series to a suitable source of time-varying voltage (not shown) such that the current in the two inner windings 86 and 89 flows in the opposite direction to the current flowing in the two outer windings 81 and 88, the direction of current flow in the outer windings being the same as the current flow in betatron windings 86-89. This results in a greater guide field intensity for a given winding current because the fields are additive within the stable orbit region. The value of the exponent n in Equation 2 in this instance depends upon the relative vertical spacings of the outer windings 81 and 88 compared to the relative vertical spacings of the inner windings 86 and 89, and the desired value may be obtained with the outer windings slightly farther apart vertically than the inner windings. The cross-sectional area of the orbital stable region will have dependent dimensions, i. e. the vertical extent may be increased by moving the windings farther apart vertically (without altering relative vertical spacings) but the horizontal extent will be decreased simultaneously and vice versa. As a practical matter, the cross-sectional area is arranged in accordance with the above considerations to be approximately as indicated by the dotted curve of Fig. 4. Windings Sii-89 are positioned as close as possible to orbital path to secure a large field at the orbit for a given current and stored energy in the windings; however, they cannot be in too close proximity because, even though the amplitude of the charged particle oscillations has been damped during the betatron start period, the charged particles still undergo some oscillation about orbital path m. Moreover, even though the charged particles are electrons and have been accelerated to nearly the Velocity of light during the betatron start period, there is a slight increase in radius of orbital path :c as a result of relatively small velocity increase during synchrotron acceleration to high energy levels.

Referring now to the exemplary circuitary of Figs. 5 and 6, the following sequence of events takes place after switch |00 of Fig. 5 is closed. As will be observed, betatron flux and field generating windings 3|-34, 'which may be series resonated with capacitors |0|, are connected to be energized in series by a time-varying source of voltage, such as alternating current source |02 and transformer |03. Peaking transformer |03al has its primary winding connected in circuit with windings 3 l-Bil, as shown, so that it will produce a voltage pulse in ts secondary circuit as the current through windings 3I-34 and the flux generated thereby goes through zero. In a few microseconds thereafter when the magnetic induction at the orbital path :I: has reached a value which causes charged particles of several kilovolts energy to be constrained thereto, such as the point a of Fig. 6 wherein the magnetic induction B in the orbital plane is plotted versus time, gun is energized by means of pulse generator |04, the initiation of which is determined by delay device m5. The charged particles which are thus introduced into orbital path a: are accelerated by the betatron flux and field generating windings ill-34 until they have reached a desired energy level, at which time -delay device |06 causes high frequency generator |01 to energize resonator l0. Within close proximity thereto, delay device |08 causes pulse generator |09 to energize synchrotron guide field windings 86'-89. This latter sequence may be arranged to occur at point b as indicated on Fig. 6. After the charged particles have been accelerated further or desired additional energy has been imparted thereto by synchrotron guide field windings [S6-89 and resonator lu, delay device may be rendered effective to deenergize high frequency generator |01 at point c whereby the charged particles spiral inwardly from orbital path :v for irnpingement upon a suitable target (not shown). Alternatively, delay device may be rendered operative after the magnetic induction peals d has been traversed, e. g. the point e on r'ig. 6, whereby the charged particles spiral outwardly and may be directed to a suitable target l2 (Fig. 2) for the production of desired effects. If the charged particles are electrons, high energy X-rays may be generated in this mannerY and extracted from tanx through a circumferential groove ||3 (big. l) within cylindrical member 48, a sion iis' in shield il (Fig. 2), anc a port mi (Fig. 2).

It will be understood by those well skilled in the art that various forms of delay devices,` pulse generators, and high frequency generators may be employed to secure the above mentioned purposes. It will also be understood that windings 3|-34 and capacitors lill may be energized in parallel by means of source H32 and transformer H03, although the above described series connection is to be preferred because harmonics in supply voltage are itered and short-circuits in windings 3|-34 are current-limited.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. Apparatus for accelerating charged particles comprising means providing a chamber within which charged particles may be accelerated along an orbital path; means for injecting said charged particles; a iirst set of windings within said chamber for accelerating said particles along said orbital path'including an outer pair of windings axially spaced on opposite sides of a plane in which said orbit lies and an inner pair of wind.- ings axially spaced on opposite sides of said plane, the space enclosed by said windings being substantially free of ferromagnetic material; means for energizing said first set of windings including a source of time-varying voltage connected thereto; said windings being spatially interrelated such that energization thereof by said source of time-varying voltage produces coinciaeeaiai dentallyboth a time-varying-m'agnetic ux which links saidfo'rbital path to initially accelerate said particles and a time-varying magnetic-guide eld which traverses said orbital path to .constrain said particles thereto; -a high frequency circuit coupled with said orbital path and operative to impart further energy to said-particles after initial acceleration by said rst set of windings; a second set of windings enclosing a space within said chamber which is substantially free of ferromagnetic material and including an outer pair of windings axially spaced on opposite sides of said plane in which said orbit lies and an inner pair of windings axially spaced on opposite sides of said plane; and a source of time-Varying voltage connected to said second set of windings; said second set of windings being spatially interrelated such that energization thereof by said lastnamed source of time-varying voltage near the time said high frequency circuit becomes `operative produces a time-varying magnetic guide eld which constrainsV said particles to said orbital path during the imparting of further energy thereto by said high frequency circuit.

2. Apparatus for accelerating charged particles comprising means providing a chamber within which charged particles may be accelerated along an essentially circular path; means for injecting charged particles within said chamber; a rst set of windings within said chamber for accelerating said charged particles along said path including two pairs of windings enclosing a space which is substantially free of ferromagnetic material, one of said pairs of windings having a diameter greater than said path and the other having a diameter less than said-path, each winding in each pair being disposed on the opposite side of a plane in which said Apath-lies in relation to the remaining winding of each respective pair; means for energizing said rst set of windings including a source of time-varying voltage connected thereto; said windings being spatially interrelated and series-connected such that ener-v gization thereof by said source of time-varying voltage produces coincidentally both a time-varying magnetic iiux which links said path to initially accelerate said particles and a time-varying magnetic guide eld which traverses said path to Yconstrain said i'particles thereto; a high frequency circuit including an electric iield producing means coupled with said path and operative'after a predetermined time to impart further energyto said particles following initial acceleration bysaid Airst s'e't Vof windings; lasecond set of windings'e'nclosing a space within said chamber which is substantially free of ferromagnetic material and including two pairs of windings, one of said pairs of windings having `a Ydiameter greater than vsaid path and the other having a diameter less than said path,'each winding in eachvpair being disposed on the opposite side of said'plane in which said'path lies in relation'to the remaining winding of 'each respective pair; anda source of time-varying voltage connected to said second set of windings; said'second set of windings being "spatially interrelated'and series-'connected such that venengization thereof by said last-named source of time-varying voltage near the time said highA frequency circuit becomes operative produces a time-varying magnetic guide eld which traverses said path and constrains 'said particles thereto during the imparting of further' energy by said high frequency circuit.

3. Apparatus for accelerating charged particles comprising means providing fa chamber within which charged particles may be'accelerated'along an orbital path; means for injecting charged particles within said chamber; betatron eld and flux generating windings supported within said chamber and having a non-ferromagnetic core, said windings including one pair of substantially coaxial windings having a diameter greater than said orbital path anda second pair of substantially coaxial windings having a diameter less than said orbital path, each winding in each'pair being disposed on the opposite side of a plane in which said orbital path lies in relation to the remaining winding of each respective pair; means for energizing said betatron windings including a source of time-varying voltage connected thereto; said windings being spatially interrelated'such that energization thereof produces conditions coincidentally satisfying the two relations:

where Ao is the total change in uX linking the orbital path from the time at which the magnetic induction B is zero, rn is the radius of the orbital path, and Bo is the magnetic induction at the orbital path; and

B *B0 n where n is an exponent having a value between 0 and l and r is the radius of a position under consideration; the energization of said betatron windings being effective to produce initial acceleration of said injected chargedparticlesalong said orbital path to a desired energy levelya high frequency circuit including an electric field generating means coupled with said orbital -path and operative following said initial `acceleration by said betatron windings to impart additional energy to said charged particles; further windings supported within said chamber and having a nonferroniagnetic core, said furtherl windings including one pair of substantially coaxial windings having a diameter greater than said orbitalpath and'a second pair of substantially coaxial windings'having a diameter less than said orbital path, each winding in each pair'being disposedvv on the opposite side of a plane in which said orbitalp'ath lies in relation to the remaining winding of` each respective pair; said further windings being spatially interrelated such that energization thereof by said last-named source of time-'varying voltage near the time saidhigh yfrequency circuit becomesoperative produces atime#varying magnetic guide field which satisfies only thesecond of said two relations and constrains said particles to said orbital path during theim-parting of further energy by said high Vfrequency-circuit.

4. Apparatus for acceleratin'gchargedparticles comprising means providing va chamber ywithin which charged particlesmay be-accelerated'along an orbital path, betatron iield and uxgenerating windings magnetically coupled with'said`1path,1a source of time-varying voltage connectedto'-said windings for energizing the same to producelcoincidentally a time-varying magnetic ''iiuxwhieh links said orbital pathandla time-var'yingflmag-V netic guide iield which traverses Said orbital path, means forprojecting charged particlesfalong said orbital path at a timed instant early in the -cycle of energization of said betatron field and "flux generating windings wherebyvr said 'particles will beV initially accelerated'by said time-varying magnetic flux while being constrained to said orbital path by Said time-varying magnetic guide field, synchrotron means for imparting further energy to said charged particles including a high frequency circuit having electric field producing means coupled with said orbital path, a source of high frequency voltage connected to said circuit for energizing the same at a timed instant later in the cycle of energization of said betatron field and flux generating windings whereby said particles will have further energy imparted thereto by said synchrotron means after initial acceleration by said betatron field and fiux generating windings, synchrotron guide field windings magnetically coupled with said path, and a source of time-varying voltage connected to said lastnamed windings for energizing the same at a timed instant near the energization of said high frequency circuit to produce with said synchrotron windings a second magnetic guide field traversing said orbital path whereby said charged particles will be constrained to said orbital path during the imparting of additional energy thereto by said synchrotron means.

5. Apparatus for accelerating charged particles comprising means providing a chamber within which charged particles may be accelerated along an orbital path, betatron field and flux generating windings magnetically coupled with said path, a source of time-varying voltage connected to said windings for energizing the same to produce coincidentally a time-varying magnetic flux which links said orbital path and a time-varying magnetic guide field which traverses said orbital path, a source of charged particles, circuit means connected to said source for energizing the same at a timed instant early in the cycle of energization of said betatron field and fiux generating windings whereby said particles will be initially accelerated by said time-varying magnetic fiux while being constrained to said orbital path by said time-varying magnetic guide field, synchrotron means for imparting further energy to said charged particles including a high frequency circuit having electric field producing means coupled with said orbital path, a source of high frequency voltage and timing means connected to said high frequency circuit for energizing said high frequency circuit at a timed instant later in the cycle of energization of said betatron flux and field generating windings whereby said particles will have further energy imparted thereto by said synchrotron means after initial acceleration by said betatron field and flux generating windings, synchrotron guide field windings magnetically coupled with said path, a source of time-varying voltage connected to said synchrotron windings, and circuit means connected to said last-named source for energizing the saine at a timed instant near the energization of said high frequency circuit to produce with said synchrotron windings a second magnetic guide field traversing said orbital path whereby said charged particles will be constrained to said orbital path during the imparting of additional energy thereto by said synchrotron means.

6. In apparatus for accelerating charged particles along an orbital path, an air-tight tank of ferromagnetic material enclosing said path, a plurality of windings insulatingly supported in spaced relationship within said tank, means for energizing said windings with time-varying current, and a liner of non-ferromagnetic material insulatingly supported within said tank and enclosing said windings for confining the time- 1'4 varying magnetic fields and fluxes generated by said windings.

'7. In apparatus for accelerating charged particles along an orbital path, an air-tight tank of ferromagnetic material enclosing said path, said tank being arranged to be evacuated, a plurality of windings insulatingly supported in spaced relation within said tank and enclosing a space substantially free of ferromagnetic material, means for energizing said windings with time-Varying current, and a liner of non-ferromagnetic material insulatingly supported within said tank and enclosing said windings for confining `the time-varying magnetic fields and fluxes generated by said windings.

8. In apparatus for accelerating charged par'-V ticles along an orbital path, an air-tight tank of ferromagnetic material enclosing said path, a plurality of windings Ainsulatingly supported in spaced relationship within said tank and defining among themselves an annular space within which said orbital path lies, means for energizing said windings with a time-varying current to provide a plurality of magnetic fields and fluxes within said tank, and an annular electrostatic shield supported within said tank and extending into said annular space defined by said windings to shield charged particles traveling along said path from the electric potentials on said windings.

9. In apparatus for accelerating charged particles along an orbital path, an air-tight tank of ferromagnetic material enclosing said path, a plurality of windings insulatingly supported in spaced relationship within said tank and defining among themselves an annular space within which said orbital path lies, said windings mutually enclosing a space substantially free of ferromagnetic material, said windings with a 4time-varying current to provide a plurality of magnetic fields and fiuxes within said tank, a liner of non-ferromagnetic material insulatingly supported within said tank and enclosing said windings for confining the time-varying magnetic fields and fluxes generated by said windings, and an electrostatic shield supported within said liner and extending into said annular space defined by said windings to shield charged particles traveling along said path from the electric potentials on said windings.

10. In apparatus for accelerating charged particles along an orbital path, an air-tight tank of ferromagnetic material enclosing said path, a plurality of windings insulatingly supported in spaced relationship within said tank and defining among themselves an annular space within which said orbital path lies, said windings mutually enclosing a space substantially free of ferromagnetic material, means for energizing said windings with a time-Varying current to provide a plurality of magnetic fields and uxes within said tank for accelerating charged particles along said path, a liner of non-ferromagnetic material insulatingly supported within said tank and enclosing said windings for confining the timevarying magnetic fields and fluxes generated by said windings, an electrostatic shield supported within said liner and extending into said annular space defined by said windings to shield charged particles traveling along said path from the electric potentials on said windings, said shield comprising la plurality of conductors depending from said liner and forming substantially an annular enclosure about said path, a plurality of conductors depending from said liner and extending into said annular enclosure formed by said shield,

means for energizingsaidz last-named plurality of conductors forming an enclosure about only a portion of said path, said first andVY second-named plurality of conductors forming the boundariesof a high frequency resonator, and means for exciting said. resonator to generate an electric eld for also accelerating chargedvparticles along said path.

l1'. Apparatus for accelerating charged particles along an orbital path comprisinga set of betatron field' and'ux generating windings positioned: adjacent the orbital path for accelerating saidparticles,along the orbital path to a predetermined energy level byy 'betatron action, a high frequency circuit coupled with the orbital path to impart synchrotron accelerationv to said particles following said betatron acceleration, and

a set of synchrotron guide eld windings posi-V t-ioned adjacentV said orbital path for constraining-said particles; to .said orbital path duringY the` period rofl said synchrotron-A acceleration.'

JAMES L. LAWSON. HOWARD R. KRATZ. GEORGE L. RAGAN.

REFERENCES CITED The followingy references are of record in the le of patent;A 

